Remove double-caching in tethered diskless

By default, the squashfs file was being cached as well as the contents after extraction.

This is superfluous pressure on the cache of the OS.

However, it does help keep the image afloat through 'confignet', so
leave it on until onboot completes, then reclaim cache and disable further caching.

confluent_osdeploy/el10-diskless/profiles/default/scripts/imageboot.sh

@@ -45,6 +45,7 @@ memtot=$(grep ^MemTotal: /proc/meminfo|awk '{print $2}')
 memtot=$((memtot/2))$(grep ^MemTotal: /proc/meminfo | awk '{print $3'})
 echo $memtot > /sys/block/zram0/disksize
 mkfs.xfs /dev/zram0 > /dev/null
+TETHERED=0
 if [ "untethered" = "$(getarg confluent_imagemethod)" ]; then
     mount -o discard /dev/zram0 /sysroot
     echo -en "Decrypting and extracting root filesystem: 0%\r"
@@ -69,6 +70,7 @@ if [ "untethered" = "$(getarg confluent_imagemethod)" ]; then
     wait
     echo -e "Decrypting and extracting root filesystem: 100%"
 else
+    TETHERED=1
     mount -o discard /dev/zram0 /mnt/overlay
     if [ ! -f /tmp/mountparts.sh ]; then
         mkdir -p /mnt/overlay/upper /mnt/overlay/work
@@ -154,6 +156,17 @@ ln -s /sysroot/lib/modules/$(uname -r) /lib/modules/
 mv /lib/firmware /lib/firmware-ramfs
 ln -s /sysroot/lib/firmware /lib/firmware
 kill $(grep -l ^/usr/lib/systemd/systemd-udevd  /proc/*/cmdline|cut -d/ -f 3)
+if [ $TETHERED -eq 1 ]; then
+    (
+        sleep 86400 &
+        ONBOOTPID=$!
+        mkdir -p /sysroot/run/confluent
+        echo $ONBOOTPID > /sysroot/run/confluent/onboot_sleep.pid
+        wait $ONBOOTPID
+        losetup $loopdev --direct-io=on
+        dd if=/mnt/remoteimg/rootimg.sfs iflag=nocache count=0 >& /dev/null
+    ) &
+fi
 if grep debugssh /proc/cmdline >& /dev/null; then
     exec /opt/confluent/bin/start_root
 else

confluent_osdeploy/el9-diskless/profiles/default/scripts/imageboot.sh

@@ -45,6 +45,7 @@ memtot=$(grep ^MemTotal: /proc/meminfo|awk '{print $2}')
 memtot=$((memtot/2))$(grep ^MemTotal: /proc/meminfo | awk '{print $3'})
 echo $memtot > /sys/block/zram0/disksize
 mkfs.xfs /dev/zram0 > /dev/null
+TETHERED=0
 if [ "untethered" = "$(getarg confluent_imagemethod)" ]; then
     mount -o discard /dev/zram0 /sysroot
     echo -en "Decrypting and extracting root filesystem: 0%\r"
@@ -69,6 +70,7 @@ if [ "untethered" = "$(getarg confluent_imagemethod)" ]; then
     wait
     echo -e "Decrypting and extracting root filesystem: 100%"
 else
+    TETHERED=1
     mount -o discard /dev/zram0 /mnt/overlay
     if [ ! -f /tmp/mountparts.sh ]; then
         mkdir -p /mnt/overlay/upper /mnt/overlay/work
@@ -156,6 +158,21 @@ mv /lib/firmware /lib/firmware-ramfs
 ln -s /sysroot/lib/firmware /lib/firmware
 rm -f /sysroot/etc/dracut.conf.d/diskless.conf # remove diskless dracut from runtime, to make kdump happier
 kill $(grep -l ^/usr/lib/systemd/systemd-udevd  /proc/*/cmdline|cut -d/ -f 3)
+if [ $TETHERED -eq 1 ]; then
+    # In tethered mode, the double-caching is useful to get through tricky part of
+    # onboot with confignet. After that, it's excessive cache usage.
+    # Give the onboot script a hook to have us come in and enable directio to the
+    # squashfs and drop the cache of the rootimg so far
+    (
+        sleep 86400 &
+        ONBOOTPID=$!
+        mkdir -p /sysroot/run/confluent
+        echo $ONBOOTPID > /sysroot/run/confluent/onboot_sleep.pid
+        wait $ONBOOTPID
+        losetup $loopdev --direct-io=on
+        dd if=/mnt/remoteimg/rootimg.sfs iflag=nocache count=0 >& /dev/null
+    ) &
+fi
 if grep debugssh /proc/cmdline >& /dev/null; then
     exec /opt/confluent/bin/start_root
 else

confluent_osdeploy/el9-diskless/profiles/default/scripts/onboot.sh

@@ -62,5 +62,11 @@ run_remote_parts onboot.d
 # Induce execution of remote configuration, e.g. ansible plays in ansible/onboot.d/
 run_remote_config onboot.d
 
+if [ -f /run/confluent/onboot_sleep.pid ]; then
+    sleeppid=$(cat /run/confluent/onboot_sleep.pid)
+    kill "$sleeppid"
+    rm -f /run/confluent/onboot_sleep.pid
+fi
+
 #curl -X POST -d 'status: booted' -H "CONFLUENT_NODENAME: $nodename" -H "CONFLUENT_APIKEY: $confluent_apikey" https://$confluent_mgr/confluent-api/self/updatestatus
 kill $logshowpid